He is 21, a handsome, charismatic Tibetan who describes being a lama as his job. He is passionately keen on music, he raps, break-dances and parties in capital cities around the globe. Kalu Rinpoche chronicles his moods, his existential angst, his activities and philosophical insights on Facebook – and he recently broke the most profoundly entrenched Tibetan Buddhist taboo with a confessional video that received more than 23,000 hits on YouTube.

It is hardly surprising that Kalu is agonising over what the future holds for him. As a baby, he was recognised as the reincarnation of the deeply revered previous Kalu, who was one of two lamas largely responsible for the worldwide explosion of interest in Tibetan Buddhism during the late 1970s and throughout the 80s.

Old Kalu was seen as a bodhisattva – a person who has attained a level of realisation similar to that of the historical Buddha. He spent 13 years in solitary retreat as a hermit yogi in eastern Tibet, before escaping to India following the Chinese invasion. Kalu had his headquarters in the Himalayan foothills, but he spent the rest of his life travelling the world, setting up meditation centres, teaching and attending to the needs of many thousands of followers.

Old Kalu died in 1989 after establishing a formidable reputation. He was an impossible act to follow, leaving his successor with responsibility for over 70 centres across four continents, together with a duty of care for the spiritual wellbeing of the people involved in them. Young Kalu's father, Gyaltsen, was old Kalu's personal assistant. In his confessional video, young Kalu says the traumatic events he experienced during his teenage years started after his father died when he was nine.

He relates how he was moved to a different monastery and at the age of 12 was sexually abused by older monks. He goes on to reveal that when he refused to obey instructions, his tutor tried to kill him.

"It was all about money, power and control," he says.

Kalu did the traditional three-year retreat from the age of 15, but after that his training came to an abrupt end. "I went crazy," he says. "I became a drug addict and an alcoholic."

Kalu's exposure on the internet of the dark underbelly of Tibetan monastic life is unprecedented in modern times. People who knew his predecessor say that he was sometimes critical in private, but the rule in lama land is that you never air your grievances to the outside world. Above all, you never cause loss of face by criticising a fellow lama in public.

The shock that reverberated across the Tibetan Buddhist community following these revelations is still making waves. In his Facebook posts, young Kalu seems undecided about what to do next. He is no longer a monk and appears to have moved on from drug and alcohol excess, but there is no teaching schedule for 2012 on his website.

The respected British lama Jampa Thaye sympathises with Kalu: "Ideally, a young incarnate lama should be given time to mature – intellectually and in contemplation," he says. "But all too often they are thrust into teaching tours in order to raise funds for their monasteries or in Kalu's case, the organisation he inherited from his predecessor." Lama Jampa points out that Kalu does not benefit from "the protective cocoon of a monastery" and also has to cope with the unrestrained adoration of his western devotees: "No wonder he's floundering. Sadly, I think his suffering will continue for some time. In my view the best thing he could do is try to live an ordinary life."

According to his recent public utterances, Kalu has this idea in mind. Instead of urging his followers into the study and long retreats essential to serious Tibetan Buddhist practice, he asks them to be kind to each other and to take care of the poor and the needy. He often talks about love and insists that he is just an ordinary person doing his best to lead a good life.

Young Kalu demonstrated his moral fibre shortly after he first arrived in France to check out the meditation centres set up by old Kalu. He discovered that one of them had been taken over by a group of corrupt Bhutanese monks, who were breaking their vows and wallowing in self-indulgence. Most of the French Buddhists who had supported the centre for many years had fled in disgust and the place was no longer functional. Horrified and distressed, Kalu ordered the monks to leave. They refused to acknowledge his authority and were only persuaded to return to Bhutan after Kalu enlisted backup from Tai Situ Rinpoche, the senior lama of his lineage.

At the age of 21, Kalu has been traumatised by an attempt on his life, sexual abuse and a massive load of expectations and responsibilities. He is a deracinated Tibetan, born in exile – and also a high-profile guru with a worldwide following. The intensity of his experiences so far highlights the cultural dissonance between Tibetan tradition and the challenges of 21st-century life in the developed world. Kalu is probably seen as a loose canon by older lamas, but he gets away with it because of his status. In one sense he is a victim, but perhaps he will turn out to be a pioneer. Or a bit of both.